The present invention relates generally to the manufacturing and machine tool industry, sometimes known as toolmaking.
There are many different methods that machinists use to hold a work-piece to a milling machine table so that machining operations and statistical measuring processes can be performed on the work-piece. Most milling machine tables have T-shaped slots that traverse the top of the table. Those slots accommodate a variety of different clamps, fixtures, grips and T-shaped bolts that are used to hold a work-piece firmly in place. The table with the attached work-piece may then be moved in three dimensions either manually or by computer (CNC) as the milling machines""cutting tool engages the work-piece. Usually, the size of work-piece itself is limited to the size of the table on the milling machine or the extent of the feature(s) being machined. In relative terms, a larger work-piece generally requires a larger milling machine which, in turn, comes equipped with a larger table with more clamping space. If the work-piece is larger than the available table, there is often no means of securing the work-piece to the table even if the individual features being machined are small enough for the smaller milling machine to produce them. Therefore, there exists a need to firmly secure a large work-piece to a smaller milling machine table such as when the size of the work-piece extends beyond the edge of the milling machine table and does not allow access to the T-slots on the top of the table.
According to its major aspects and briefly stated, the present invention is a clamping device for securing an oversized work-piece to a milling machine table, especially to a smaller milling machine table. Whereas conventional clamping methods make use of the T-slots on the top of the table, this invention makes use of the T-slot that is typically located on the front of all Bridgeport-type milling machine tables along a plane perpendicular to and offset from the working plane defined by the table on which milling work-pieces are typically mounted. The existing front T-slot comes as a standard feature on Bridgeport-type milling machines and is most often used for securing moveable, mechanical limit switches. The limit switches are used in automated machining operations to define the stopping end-points for the table when it moves through machining cycles.
The primary feature of the present invention is the ability to make use of the front T-slot on the table to hold a work-piece to the table. The present invention is a clamp that is secured to the table using this front T-slot. The clamp is capable of holding an oversized work-piece to the table without having access to any of the top surface T-slots that are typically used for clamping. A part of the clamp called the xe2x80x9cheel blockxe2x80x9d attaches to the table""s front T-slot, which is located in a plane perpendicular to the table""s surface, below both the working surface of the table and the work-piece. The heel block extends away from the table and beyond the work-piece. Running parallel with and bolted to the heel block is a clamping block. The bolts holding the clamping block extend from the heel block, past the work-piece, to separate the heel block and clamping block apart by a little more than the thickness of the work-piece. The clamping block then extends parallel to the heel block and above the work-piece that is on the table. The bolts are then adjusted and tightened to provide the desired clamping effect on the work-piece.
An important feature of the present invention is the shape of the end of the heel block. The heel block is shaped to securely fit into the front T-slot so that this slot can be used in lieu of top surface slots. The shape may allow the clamp to be inserted from the end of the T-slot or, in an alternative embodiment, directly in using a slight rotation of the clamp.
One feature of the present invention is the use of multiple tapped holes in one or both of the blocks. This allows for flexibility in mounting work-pieces of different size as well as different degrees of leverage to be applied to the work-piece.
An additional feature of the present invention is a minimal number of tapped holes in either block and the use of slots instead of holes. When slots are used, the tightening bolt has a head on one end and a nut on the other end for compressing the system.
In the case of either slots or holes, one of the bolts (for example, the separation bolt) is merely used as a spacer. It screws into a tapped hole on one of the two blocks to hold itself in position while applying tension on the other bolt (the tightening bolt), thus putting the entire system into compression and holding the work-piece firmly on the table. The actual configuration of the bolts can be varied depending on the needs of the work-piece. Clearly, the separation bolt only needs to be threaded on one end as its other end is used as a dead-stop on the heel block.
Another advantage of the present invention is the fact that one set of clamps fits a wide range of work-pieces because of the use of slots cut on either the heel block, the clamping block, or on both. By putting slots on the preferred embodiment, the clamping block can be adjusted back and forth to hold work-pieces of a wide variety of sizes.
It will be apparent to anyone skilled in the art of machining that several different sizes of clamps and bolts can be used to clamp a large variety of different work-pieces. It will also be apparent to anyone skilled in the art that multiple clamps can and should be used to properly hold a work-piece.